Fexofenadine hydrochloride (4-[1-hydroxy-4-[4-(hydroxydiphenylmethyl)-1-piperidinyl]butyl]-α,α-dimethylphenylacetic acid hydrochloride) has formula (I) below:
and is licensed by the US Food and Drug Administration (FDA) as an antihistamine, antiallergic and bronchodilator under the trade name Allegra®.
WO-A-95/31437 describes the preparation of hydrated polymorphs, or pseudo-morphs, of fexofenadine hydrochloride (form II and form IV) and their conversion to non-hydrated polymorphous forms (form I and form III) by azeotropic distillation or water-minimizing recrystallization.
WO-A-00/71124 describes amorphous, presumably non-hydrated fexofenadine hydrochloride and its preparation, a spray drying or freeze drying being carried out as the final stage.